Sequence based short code design for resource spread multiple access (RSMA)

ABSTRACT

Aspects of the present disclosure provide design that allows for assigning code sequences for UEs for use in RSMA.

CLAIM OF PRIORITY UNDER 35 U.S.C. § 119

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 62/617,039, filed Jan. 12, 2018, which is hereinincorporated by reference in its entirety.

FIELD

The present disclosure relates generally to wireless communicationsystems, and more particularly, to a design for sequences to assign touser equipments (UEs) for multi-layer Resource Spread Multiple Access(RSMA).

BACKGROUND

Wireless communication systems are widely deployed to provide varioustelecommunication services such as telephony, video, data, messaging,and broadcasts. Typical wireless communication systems may employmultiple-access technologies capable of supporting communication withmultiple users by sharing available system resources (e.g., bandwidth,transmit power). Examples of such multiple-access technologies includeLong Term Evolution (LTE) systems, code division multiple access (CDMA)systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, orthogonal frequency divisionmultiple access (OFDMA) systems, single-carrier frequency divisionmultiple access (SC-FDMA) systems, and time division synchronous codedivision multiple access (TD-SCDMA) systems.

In some examples, a wireless multiple-access communication system mayinclude a number of base stations, each simultaneously supportingcommunication for multiple communication devices, otherwise known asuser equipment (UEs). In LTE or LTE-A network, a set of one or more basestations may define an eNodeB (eNB). In other examples (e.g., in a nextgeneration or 5^(th) generation (5G) network), a wireless multipleaccess communication system may include a number of distributed units(DUs) (e.g., edge units (EUs), edge nodes (ENs), radio heads (RHs),smart radio heads (SRHs), transmission reception points (TRPs), etc.) incommunication with a number of central units (CUs) (e.g., central nodes(CNs), access node controllers (ANCs), etc.), where a set of one or moredistributed units, in communication with a central unit, may define anaccess node (e.g., a new radio base station (NR BS), a new radio node-B(NR NB), a network node, 5G NB, eNB, etc.). A base station or DU maycommunicate with a set of UEs on downlink channels (e.g., fortransmissions from a base station or to a UE) and uplink channels (e.g.,for transmissions from a UE to a base station or distributed unit).

These multiple access technologies have been adopted in varioustelecommunication standards to provide a common protocol that enablesdifferent wireless devices to communicate on a municipal, national,regional, and even global level. An example of an emergingtelecommunication standard is new radio (NR), for example, 5G radioaccess. NR is a set of enhancements to the LTE mobile standardpromulgated by Third Generation Partnership Project (3GPP). It isdesigned to better support mobile broadband Internet access by improvingspectral efficiency, lowering costs, improving services, making use ofnew spectrum, and better integrating with other open standards usingOFDMA with a cyclic prefix (CP) on the downlink (DL) and on the uplink(UL) as well as support beamforming, multiple-input multiple-output(MIMO) antenna technology, and carrier aggregation.

However, as the demand for mobile broadband access continues toincrease, there exists a desire for further improvements in NRtechnology. Preferably, these improvements should be applicable to othermulti-access technologies and the telecommunication standards thatemploy these technologies.

SUMMARY

The systems, methods, and devices of the disclosure each have severalaspects, no single one of which is solely responsible for its desirableattributes. Without limiting the scope of this disclosure as expressedby the claims which follow, some features will now be discussed briefly.After considering this discussion, and particularly after reading thesection entitled “Detailed Description” one will understand how thefeatures of this disclosure provide advantages that include improvedcommunications between access points and stations in a wireless network.

Certain aspects of the present disclosure provide a method for wirelesscommunications by a User Equipment (UE). The method generally includesselecting a scrambling sequence, from a set of sequences designed tomeet one or more criteria for low cross correlation across the sequencesin the set and depends on a spreading factor (SF) and number of UEs (N)in a set of UEs including the UE and using the selected scramblingsequence to scramble an transmission to a base station.

Certain aspects of the present disclosure provide a method for wirelesscommunications by a Base Station (BS). The method generally includesassigning a set of sequences to a set of user equipments (UEs), whereinthe set of sequences is designed to meet one or more criteria for lowcross correlation across the sequences in the set and depends on aspreading factor (SF) and number of UEs (N), receiving a signalincluding transmissions from one or more of the set of UEs, wherein eachtransmission from a UE is scrambled using one of the sequences in theset as a scrambling sequence, determining, for each transmission, thescrambling sequence, and decoding each transmission based on thedetermined scrambling sequence.

Aspects generally include methods, apparatus, systems, computer readablemediums, and processing systems, as substantially described herein withreference to and as illustrated by the accompanying drawings.

To the accomplishment of the foregoing and related ends, the one or moreaspects comprise the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe annexed drawings set forth in detail certain illustrative featuresof the one or more aspects. These features are indicative, however, ofbut a few of the various ways in which the principles of various aspectsmay be employed, and this description is intended to include all suchaspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description,briefly summarized above, may be had by reference to aspects, some ofwhich are illustrated in the appended drawings. It is to be noted,however, that the appended drawings illustrate only certain typicalaspects of this disclosure and are therefore not to be consideredlimiting of its scope, for the description may admit to other equallyeffective aspects.

FIG. 1 is a block diagram conceptually illustrating an exampletelecommunications system, in accordance with certain aspects of thepresent disclosure.

FIG. 2 is a block diagram illustrating an example logical architectureof a distributed RAN, in accordance with certain aspects of the presentdisclosure.

FIG. 3 is a diagram illustrating an example physical architecture of adistributed RAN, in accordance with certain aspects of the presentdisclosure.

FIG. 4 is a block diagram conceptually illustrating a design of anexample BS and user equipment (UE), in accordance with certain aspectsof the present disclosure.

FIG. 5 is a diagram showing examples for implementing a communicationprotocol stack, in accordance with certain aspects of the presentdisclosure.

FIG. 6 illustrates an example of a downlink-centric (DL-centric)subframe, in accordance with certain aspects of the present disclosure.

FIG. 7 illustrates an example of an uplink-centric (UL-centric)subframe, in accordance with certain aspects of the present disclosure.

FIG. 8 illustrates an example design 800 for generating a multi-layerRSMA modulated stream.

FIG. 9 illustrates operations 900 performed by a base station (e.g.,gNB), in accordance with certain aspects of the present disclosure.

FIG. 10 illustrates example operations 1000 performed by a UE, inaccordance with certain aspects of the present disclosure.

FIGS. 11-14 illustrate example sequences for a pair of a number of UEsand spreading factor, in accordance with certain aspects of the presentdisclosure.

FIG. 15 illustrates an example equation for generating the sequencesshown in FIGS. 11-14.

FIGS. 16-19 illustrate example sequences for a pair of a number of UEsand spreading factor, in accordance with certain aspects of the presentdisclosure.

FIG. 20 illustrates an example equation for generating the sequencesshown in FIGS. 16-19.

FIG. 21 illustrates an example generic equation for generating sequencesfor different pairs of numbers of UEs and spreading factors.

FIGS. 22-26 illustrate tables showing achievable cross-correlationvalues for different pairs of numbers of UEs and spreading factors.

FIG. 27 illustrates an example generic equation for generating sequencesfor different pairs of numbers of UEs and spreading factors and anoffset factor F.

FIGS. 28-31 illustrate example sequences for a pair of a number of UEsand spreading factor and an offset value, in accordance with certainaspects of the present disclosure.

FIG. 32 illustrates an example equation for generating the sequencesshown in FIGS. 28-31.

FIG. 33 illustrates a table showing achievable cross-correlation valuesfor different values for numbers of UEs, a single spreading factor andsingle offset value.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in one aspectmay be beneficially utilized on other aspects without specificrecitation.

DETAILED DESCRIPTION

Non-orthogonal multiple access (NMA) allows the simultaneoustransmission of more than one layer of data for more than one UE withouttime, frequency or spatial domain separation. Different layers of datamay be separated by utilizing interference cancellation or iterativedetection at the receiver. It has been agreed that NMA should beinvestigated for diversified 5G usage scenarios and use cases and 5Gshould target to support uplink NMA.

In an uplink NMA system, signal transmitter and receiver are jointlyoptimized, so that multiple layers of data from more than one UE can besimultaneously delivered in the same resource. At the transmitter side,the information of different UEs can be delivered using the same time,frequency and spatial resource. At the receiver side, the information ofdifferent UEs can be recovered by advanced receivers such asinterference cancellation or iterative detection receivers.

A key characteristic of the scrambling based NMA schemes is thatdifferent scrambling sequences are used to distinguish between differentUEs, and that an successive interference cancellation (SIC) algorithm isapplied at the BS receiver to separate different UEs. Resource SpreadMultiple Access (RSMA) is one example of a scrambling based NMA scheme.In RSMA, a group of different UEs' signals are super positioned on topof each other, and each UE's signal is spread to the entirefrequency/time resource assigned for the group. RSMA uses thecombination of low rate channel codes and scrambling codes with goodcorrelation properties to separate different UEs' signals.

In certain aspects, several different uplink multiplexing scenarios maybe considered for non-orthogonal multiple access (NMA). One example NMAscheme may include a grantless NMA scheme that does not include networkassignments or grants of scrambling sequences. In certain aspects,another example NMA scheme may include a grant based NMA scheme thatincludes network assignment of scrambling sequences.

Certain aspects of the present disclosure discuss a two stage techniquefor generating, transmitting and decoding RSMA modulated streamsincluding multi-layer RSMA modulated streams. These techniques include atwo stage technique for generating, transmitting and decoding RSMAmodulated streams including multi-layer RSMA streams on the uplink. Inan aspect, the two stage technique includes two separate stages ofscrambling one or more data streams, the two stages using differenttypes of scrambling sequences with different lengths. In certainaspects, the two stage scrambling design for RSMA modulated streams maybe used for both grant based and grantless scenarios.

NR may support various wireless communication services, such as Enhancedmobile broadband (eMBB) targeting wide bandwidth (e.g. 80 MHz beyond),millimeter wave (mmW) targeting high carrier frequency (e.g. 60 GHz),massive MTC (mMTC) targeting non-backward compatible MTC techniques,and/or mission critical targeting ultra-reliable low latencycommunications (URLLC). These services may include latency andreliability requirements. These services may also have differenttransmission time intervals (TTI) to meet respective quality of service(QoS) requirements. In addition, these services may co-exist in the samesubframe.

The following description provides examples, and is not limiting of thescope, applicability, or examples set forth in the claims. Changes maybe made in the function and arrangement of elements discussed withoutdeparting from the scope of the disclosure. Various examples may omit,substitute, or add various procedures or components as appropriate. Forinstance, the methods described may be performed in an order differentfrom that described, and various steps may be added, omitted, orcombined. Also, features described with respect to some examples may becombined in some other examples. For example, an apparatus may beimplemented or a method may be practiced using any number of the aspectsset forth herein. In addition, the scope of the disclosure is intendedto cover such an apparatus or method which is practiced using otherstructure, functionality, or structure and functionality in addition toor other than the various aspects of the disclosure set forth herein. Itshould be understood that any aspect of the disclosure disclosed hereinmay be embodied by one or more elements of a claim. The word “exemplary”is used herein to mean “serving as an example, instance, orillustration.” Any aspect described herein as “exemplary” is notnecessarily to be construed as preferred or advantageous over otheraspects.

The techniques described herein may be used for various wirelesscommunication networks such as LTE, CDMA, TDMA, FDMA, OFDMA, SC-FDMA andother networks. The terms “network” and “system” are often usedinterchangeably. A CDMA network may implement a radio technology such asUniversal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includesWideband CDMA (WCDMA) and other variants of CDMA. cdma2000 coversIS-2000, IS-95 and IS-856 standards. A TDMA network may implement aradio technology such as Global System for Mobile Communications (GSM).An OFDMA network may implement a radio technology such as NR (e.g. 5GRA), Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11(Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, etc. UTRA andE-UTRA are part of Universal Mobile Telecommunication System (UMTS). NRis an emerging wireless communications technology under development inconjunction with the 5G Technology Forum (5GTF). 3GPP Long TermEvolution (LTE) and LTE-Advanced (LTE-A) are releases of UMTS that useE-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described indocuments from an organization named “3rd Generation PartnershipProject” (3GPP). cdma2000 and UMB are described in documents from anorganization named “3rd Generation Partnership Project 2” (3GPP2). Thetechniques described herein may be used for the wireless networks andradio technologies mentioned above as well as other wireless networksand radio technologies. For clarity, while aspects may be describedherein using terminology commonly associated with 3G and/or 4G wirelesstechnologies, aspects of the present disclosure can be applied in othergeneration-based communication systems, such as 5G and later, includingNR technologies.

Example Wireless Communications System

FIG. 1 illustrates an example wireless network 100, such as a new radio(NR) or 5G network, in which aspects of the present disclosure may beperformed. For example, BSs 110 and UEs 120 may be configured to performoperations described herein with reference to FIG. 9 and FIG. 10,respectively.

As illustrated in FIG. 1, the wireless network 100 may include a numberof BSs 110 and other network entities. A BS may be a station thatcommunicates with UEs. Each BS 110 may provide communication coveragefor a particular geographic area. In 3GPP, the term “cell” can refer toa coverage area of a Node B and/or a Node B subsystem serving thiscoverage area, depending on the context in which the term is used. In NRsystems, the term “cell” and eNB, Node B, 5G NB, AP, NR BS, NR BS, orTRP may be interchangeable. In some examples, a cell may not necessarilybe stationary, and the geographic area of the cell may move according tothe location of a mobile base station. In some examples, the basestations may be interconnected to one another and/or to one or moreother base stations or network nodes (not shown) in the wireless network100 through various types of backhaul interfaces such as a directphysical connection, a virtual network, or the like using any suitabletransport network.

In general, any number of wireless networks may be deployed in a givengeographic area. Each wireless network may support a particular radioaccess technology (RAT) and may operate on one or more frequencies. ARAT may also be referred to as a radio technology, an air interface,etc. A frequency may also be referred to as a carrier, a frequencychannel, etc. Each frequency may support a single RAT in a givengeographic area in order to avoid interference between wireless networksof different RATs. In some cases, NR or 5G RAT networks may be deployed.

A BS may provide communication coverage for a macro cell, a pico cell, afemto cell, and/or other types of cell. A macro cell may cover arelatively large geographic area (e.g., several kilometers in radius)and may allow unrestricted access by UEs with service subscription. Apico cell may cover a relatively small geographic area and may allowunrestricted access by UEs with service subscription. A femto cell maycover a relatively small geographic area (e.g., a home) and may allowrestricted access by UEs having association with the femto cell (e.g.,UEs in a Closed Subscriber Group (CSG), UEs for users in the home,etc.). A BS for a macro cell may be referred to as a macro BS. A BS fora pico cell may be referred to as a pico BS. A BS for a femto cell maybe referred to as a femto BS or a home BS. In the example shown in FIG.1, the BSs 110 a, 110 b and 110 c may be macro BSs for the macro cells102 a, 102 b and 102 c, respectively. The BS 110 x may be a pico BS fora pico cell 102 x. The BSs 110 y and 110 z may be femto BS for the femtocells 102 y and 102 z, respectively. A BS may support one or multiple(e.g., three) cells.

The wireless network 100 may also include relay stations. A relaystation is a station that receives a transmission of data and/or otherinformation from an upstream station (e.g., a BS or a UE) and sends atransmission of the data and/or other information to a downstreamstation (e.g., a UE or a BS). A relay station may also be a UE thatrelays transmissions for other UEs. In the example shown in FIG. 1, arelay station 110 r may communicate with the BS 110 a and a UE 120 r inorder to facilitate communication between the BS 110 a and the UE 120 r.A relay station may also be referred to as a relay BS, a relay, etc.

The wireless network 100 may be a heterogeneous network that includesBSs of different types, e.g., macro BS, pico BS, femto BS, relays, etc.These different types of BSs may have different transmit power levels,different coverage areas, and different impact on interference in thewireless network 100. For example, macro BS may have a high transmitpower level (e.g., 20 Watts) whereas pico BS, femto BS, and relays mayhave a lower transmit power level (e.g., 1 Watt).

The wireless network 100 may support synchronous or asynchronousoperation. For synchronous operation, the BSs may have similar frametiming, and transmissions from different BSs may be approximatelyaligned in time. For asynchronous operation, the BSs may have differentframe timing, and transmissions from different BSs may not be aligned intime. The techniques described herein may be used for both synchronousand asynchronous operation.

A network controller 130 may be coupled to a set of BSs and providecoordination and control for these BSs. The network controller 130 maycommunicate with the BSs 110 via a backhaul. The BSs 110 may alsocommunicate with one another, e.g., directly or indirectly via wirelessor wireline backhaul.

The UEs 120 (e.g., 120 x, 120 y, etc.) may be dispersed throughout thewireless network 100, and each UE may be stationary or mobile. A UE mayalso be referred to as a mobile station, a terminal, an access terminal,a subscriber unit, a station, a Customer Premises Equipment (CPE), acellular phone, a smart phone, a personal digital assistant (PDA), awireless modem, a wireless communication device, a handheld device, alaptop computer, a cordless phone, a wireless local loop (WLL) station,a tablet, a camera, a gaming device, a netbook, a smartbook, anultrabook, a medical device or medical equipment, a biometricsensor/device, a healthcare device, a medical device, a wearable devicesuch as a smart watch, smart clothing, smart glasses, virtual realitygoggles, a smart wrist band, smart jewelry (e.g., a smart ring, a smartbracelet, etc.), an entertainment device (e.g., a music device, a gamingdevice, a video device, a satellite radio, etc.), a vehicular componentor sensor, a smart meter/sensor, industrial manufacturing equipment, apositioning device (e.g., GPS, Beidou, GLONASS, Galileo,terrestrial-based), or any other suitable device that is configured tocommunicate via a wireless or wired medium. Some UEs may be consideredmachine-type communication (MTC) devices or enhanced or evolved MTC(eMTC) devices.

MTC may refer to communication involving at least one remote device onat least one end of the communication and may include forms of datacommunication which involve one or more entities that do not necessarilyneed human interaction. MTC UEs may include UEs that are capable of MTCcommunications with MTC servers and/or other MTC devices through PublicLand Mobile Networks (PLMN), for example. Some UEs may be consideredInternet of Things devices. The Internet of Things (IoT) is a network ofphysical objects or “things” embedded with, e.g., electronics, software,sensors, and network connectivity, which enable these objects to collectand exchange data. The Internet of Things allows objects to be sensedand controlled remotely across existing network infrastructure, creatingopportunities for more direct integration between the physical world andcomputer-based systems, and resulting in improved efficiency, accuracyand economic benefit. When IoT is augmented with sensors and actuators,the technology becomes an instance of the more general class ofcyber-physical systems, which also encompasses technologies such assmart grids, smart homes, intelligent transportation and smart cities.Each “thing” is generally uniquely identifiable through its embeddedcomputing system but is able to interoperate within the existingInternet infrastructure. Narrowband IoT (NB-IoT) is a technology beingstandardized by the 3GPP standards body. This technology is a narrowbandradio technology specially designed for the IoT, hence its name. Specialfocuses of this standard are on indoor coverage, low cost, long batterylife and large number of devices. MTC/eMTC and/or IoT UEs include, forexample, robots, drones, remote devices, sensors, meters, monitors,location tags, etc., that may communicate with a BS, another device(e.g., remote device), or some other entity. A wireless node mayprovide, for example, connectivity for or to a network (e.g., a widearea network such as Internet or a cellular network) via a wired orwireless communication link. In FIG. 1, a solid line with double arrowsindicates desired transmissions between a UE and a serving BS, which isa BS designated to serve the UE on the downlink and/or uplink. A dashedline with double arrows indicates interfering transmissions between a UEand a BS.

Certain wireless networks (e.g., LTE) utilize orthogonal frequencydivision multiplexing (OFDM) on the downlink and single-carrierfrequency division multiplexing (SC-FDM) on the uplink. OFDM and SC-FDMpartition the system bandwidth (e.g., system frequency band) intomultiple (K) orthogonal subcarriers, which are also commonly referred toas tones, bins, etc. Each subcarrier may be modulated with data. Ingeneral, modulation symbols are sent in the frequency domain with OFDMand in the time domain with SC-FDM. The spacing between adjacentsubcarriers may be fixed, and the total number of subcarriers (K) may bedependent on the system bandwidth. For example, the spacing of thesubcarriers may be 15 kHz and the minimum resource allocation (called a‘resource block’) may be 12 subcarriers (or 180 kHz). Consequently, thenominal FFT size may be equal to 128, 256, 512, 1024 or 2048 for systembandwidth of 1.25, 2.5, 5, 10 or 20 megahertz (MHz), respectively. Thesystem bandwidth may also be partitioned into subbands. For example, asubband may cover 1.08 MHz (i.e., 6 resource blocks), and there may be1, 2, 4, 8 or 16 subbands for system bandwidth of 1.25, 2.5, 5, 10 or 20MHz, respectively.

While aspects of the examples described herein may be associated withLTE technologies, aspects of the present disclosure may be applicablewith other wireless communications systems, such as NR. NR may utilizeOFDM with a CP on the uplink and downlink and include support forhalf-duplex operation using time division duplex (TDD). A singlecomponent carrier bandwidth of 100 MHz may be supported. NR resourceblocks may span 12 sub-carriers with a sub-carrier bandwidth of 75 kHzover a 0.1 ms duration. Each radio frame may consist of 50 subframeswith a length of 10 ms. Consequently, each subframe may have a length of0.2 ms. Each subframe may indicate a link direction (i.e., DL or UL) fordata transmission and the link direction for each subframe may bedynamically switched. Each subframe may include DL/UL data as well asDL/UL control data. UL and DL subframes for NR may be as described inmore detail below with respect to FIGS. 6 and 7. Beamforming may besupported and beam direction may be dynamically configured. MIMOtransmissions with precoding may also be supported. MIMO configurationsin the DL may support up to 8 transmit antennas with multi-layer DLtransmissions up to 8 streams and up to 2 streams per UE. Multi-layertransmissions with up to 2 streams per UE may be supported. Aggregationof multiple cells may be supported with up to 8 serving cells.Alternatively, NR may support a different air interface, other than anOFDM-based. NR networks may include entities such CUs and/or DUs.

In some examples, access to the air interface may be scheduled, whereina scheduling entity (e.g., a base station) allocates resources forcommunication among some or all devices and equipment within its servicearea or cell. Within the present disclosure, as discussed further below,the scheduling entity may be responsible for scheduling, assigning,reconfiguring, and releasing resources for one or more subordinateentities. That is, for scheduled communication, subordinate entitiesutilize resources allocated by the scheduling entity. Base stations arenot the only entities that may function as a scheduling entity. That is,in some examples, a UE may function as a scheduling entity, schedulingresources for one or more subordinate entities (e.g., one or more otherUEs). In this example, the UE is functioning as a scheduling entity, andother UEs utilize resources scheduled by the UE for wirelesscommunication. A UE may function as a scheduling entity in apeer-to-peer (P2P) network, and/or in a mesh network. In a mesh networkexample, UEs may optionally communicate directly with one another inaddition to communicating with the scheduling entity.

Thus, in a wireless communication network with a scheduled access totime-frequency resources and having a cellular configuration, a P2Pconfiguration, and a mesh configuration, a scheduling entity and one ormore subordinate entities may communicate utilizing the scheduledresources.

As noted above, a RAN may include a CU and DUs. A NR BS (e.g., eNB, 5GNode B, Node B, transmission reception point (TRP), access point (AP))may correspond to one or multiple BSs. NR cells can be configured asaccess cell (ACells) or data only cells (DCells). For example, the RAN(e.g., a central unit or distributed unit) can configure the cells.DCells may be cells used for carrier aggregation or dual connectivity,but not used for initial access, cell selection/reselection, orhandover. In some cases DCells may not transmit synchronizationsignals—in some case cases DCells may transmit SS. NR BSs may transmitdownlink signals to UEs indicating the cell type. Based on the cell typeindication, the UE may communicate with the NR BS. For example, the UEmay determine NR BSs to consider for cell selection, access, handover,and/or measurement based on the indicated cell type.

FIG. 2 illustrates an example logical architecture of a distributedradio access network (RAN) 200, which may be implemented in the wirelesscommunication system illustrated in FIG. 1. A 5G access node 206 mayinclude an access node controller (ANC) 202. The ANC may be a centralunit (CU) of the distributed RAN 200. The backhaul interface to the nextgeneration core network (NG-CN) 204 may terminate at the ANC. Thebackhaul interface to neighboring next generation access nodes (NG-ANs)may terminate at the ANC. The ANC may include one or more TRPs 208(which may also be referred to as BSs, NR BSs, Node Bs, 5G NBs, APs, orsome other term). As described above, a TRP may be used interchangeablywith “cell.”

The TRPs 208 may be a DU. The TRPs may be connected to one ANC (ANC 202)or more than one ANC (not illustrated). For example, for RAN sharing,radio as a service (RaaS), and service specific AND deployments, the TRPmay be connected to more than one ANC. A TRP may include one or moreantenna ports. The TRPs may be configured to individually (e.g., dynamicselection) or jointly (e.g., joint transmission) serve traffic to a UE.

The local architecture 200 may be used to illustrate fronthauldefinition. The architecture may be defined that support fronthaulingsolutions across different deployment types. For example, thearchitecture may be based on transmit network capabilities (e.g.,bandwidth, latency, and/or jitter).

The architecture may share features and/or components with LTE.According to aspects, the next generation AN (NG-AN) 210 may supportdual connectivity with NR. The NG-AN may share a common fronthaul forLTE and NR.

The architecture may enable cooperation between and among TRPs 208. Forexample, cooperation may be preset within a TRP and/or across TRPs viathe ANC 202. According to aspects, no inter-TRP interface may beneeded/present.

According to aspects, a dynamic configuration of split logical functionsmay be present within the architecture 200. As will be described in moredetail with reference to FIG. 5, the Radio Resource Control (RRC) layer,Packet Data Convergence Protocol (PDCP) layer, Radio Link Control (RLC)layer, Medium Access Control (MAC) layer, and a Physical (PHY) layersmay be adaptably placed at the DU or CU (e.g., TRP or ANC,respectively). According to certain aspects, a BS may include a centralunit (CU) (e.g., ANC 202) and/or one or more distributed units (e.g.,one or more TRPs 208).

FIG. 3 illustrates an example physical architecture of a distributed RAN300, according to aspects of the present disclosure. A centralized corenetwork unit (C-CU) 302 may host core network functions. The C-CU may becentrally deployed. C-CU functionality may be offloaded (e.g., toadvanced wireless services (AWS)), in an effort to handle peak capacity.

A centralized RAN unit (C-RU) 304 may host one or more ANC functions.Optionally, the C-RU may host core network functions locally. The C-RUmay have distributed deployment. The C-RU may be closer to the networkedge.

A DU 306 may host one or more TRPs (edge node (EN), an edge unit (EU), aradio head (RH), a smart radio head (SRH), or the like). The DU may belocated at edges of the network with radio frequency (RF) functionality.

FIG. 4 illustrates example components of the BS 110 and UE 120illustrated in FIG. 1, which may be used to implement aspects of thepresent disclosure. As described above, the BS may include a TRP. One ormore components of the BS 110 and UE 120 may be used to practice aspectsof the present disclosure. For example, antennas 452, Tx/Rx 222,processors 466, 458, 464, and/or controller/processor 480 of the UE 120and/or antennas 434, processors 460, 420, 438, and/orcontroller/processor 440 of the BS 110 may be used to perform theoperations described herein and illustrated with reference to FIGS.8-11.

FIG. 4 shows a block diagram of a design of a BS 110 and a UE 120, whichmay be one of the BSs and one of the UEs in FIG. 1. For a restrictedassociation scenario, the base station 110 may be the macro BS 110 c inFIG. 1, and the UE 120 may be the UE 120 y. The base station 110 mayalso be a base station of some other type. The base station 110 may beequipped with antennas 434 a through 434 t, and the UE 120 may beequipped with antennas 452 a through 452 r.

At the base station 110, a transmit processor 420 may receive data froma data source 412 and control information from a controller/processor440. The control information may be for the Physical Broadcast Channel(PBCH), Physical Control Format Indicator Channel (PCFICH), PhysicalHybrid ARQ Indicator Channel (PHICH), Physical Downlink Control Channel(PDCCH), etc. The data may be for the Physical Downlink Shared Channel(PDSCH), etc. The processor 420 may process (e.g., encode and symbolmap) the data and control information to obtain data symbols and controlsymbols, respectively. The processor 420 may also generate referencesymbols, e.g., for the PSS, SSS, and cell-specific reference signal. Atransmit (TX) multiple-input multiple-output (MIMO) processor 430 mayperform spatial processing (e.g., precoding) on the data symbols, thecontrol symbols, and/or the reference symbols, if applicable, and mayprovide output symbol streams to the modulators (MODs) 432 a through 432t. For example, the TX MIMO processor 430 may perform certain aspectsdescribed herein for RS multiplexing. Each modulator 432 may process arespective output symbol stream (e.g., for OFDM, etc.) to obtain anoutput sample stream. Each modulator 432 may further process (e.g.,convert to analog, amplify, filter, and upconvert) the output samplestream to obtain a downlink signal. Downlink signals from modulators 432a through 432 t may be transmitted via the antennas 434 a through 434 t,respectively.

At the UE 120, the antennas 452 a through 452 r may receive the downlinksignals from the base station 110 and may provide received signals tothe demodulators (DEMODs) 454 a through 454 r, respectively. Eachdemodulator 454 may condition (e.g., filter, amplify, downconvert, anddigitize) a respective received signal to obtain input samples. Eachdemodulator 454 may further process the input samples (e.g., for OFDM,etc.) to obtain received symbols. A MIMO detector 456 may obtainreceived symbols from all the demodulators 454 a through 454 r, performMIMO detection on the received symbols if applicable, and providedetected symbols. For example, MIMO detector 456 may provide detected RStransmitted using techniques described herein. A receive processor 458may process (e.g., demodulate, deinterleave, and decode) the detectedsymbols, provide decoded data for the UE 120 to a data sink 460, andprovide decoded control information to a controller/processor 480.According to one or more cases, CoMP aspects can include providing theantennas, as well as some Tx/Rx functionalities, such that they residein distributed units. For example, some Tx/Rx processing can be done inthe central unit, while other processing can be done at the distributedunits. For example, in accordance with one or more aspects as shown inthe diagram, the BS mod/demod 432 may be in the distributed units.

On the uplink, at the UE 120, a transmit processor 464 may receive andprocess data (e.g., for the Physical Uplink Shared Channel (PUSCH)) froma data source 462 and control information (e.g., for the Physical UplinkControl Channel (PUCCH) from the controller/processor 480. The transmitprocessor 464 may also generate reference symbols for a referencesignal. The symbols from the transmit processor 464 may be precoded by aTX MIMO processor 466 if applicable, further processed by thedemodulators 454 a through 454 r (e.g., for SC-FDM, etc.), andtransmitted to the base station 110. At the BS 110, the uplink signalsfrom the UE 120 may be received by the antennas 434, processed by themodulators 432, detected by a MIMO detector 436 if applicable, andfurther processed by a receive processor 438 to obtain decoded data andcontrol information sent by the UE 120. The receive processor 438 mayprovide the decoded data to a data sink 439 and the decoded controlinformation to the controller/processor 440.

The controllers/processors 440 and 480 may direct the operation at thebase station 110 and the UE 120, respectively. The processor 440 and/orother processors and modules at the base station 110 may perform ordirect, e.g., the processes for the techniques described herein. Theprocessor 480 and/or other processors and modules at the UE 120 may alsoperform or direct, e.g., execution of the functional blocks illustratedin FIG. 10, and/or other processes for the techniques described herein.The memories 442 and 482 may store data and program codes for the BS 110and the UE 120, respectively. A scheduler 444 may schedule UEs for datatransmission on the downlink and/or uplink.

FIG. 5 illustrates a diagram 500 showing examples for implementing acommunications protocol stack, according to aspects of the presentdisclosure. The illustrated communications protocol stacks may beimplemented by devices operating in a in a 5G system (e.g., a systemthat supports uplink-based mobility). Diagram 500 illustrates acommunications protocol stack including a Radio Resource Control (RRC)layer 510, a Packet Data Convergence Protocol (PDCP) layer 515, a RadioLink Control (RLC) layer 520, a Medium Access Control (MAC) layer 525,and a Physical (PHY) layer 530. In various examples the layers of aprotocol stack may be implemented as separate modules of software,portions of a processor or ASIC, portions of non-collocated devicesconnected by a communications link, or various combinations thereof.Collocated and non-collocated implementations may be used, for example,in a protocol stack for a network access device (e.g., ANs, CUs, and/orDUs) or a UE.

A first option 505-a shows a split implementation of a protocol stack,in which implementation of the protocol stack is split between acentralized network access device (e.g., an ANC 202 in FIG. 2) anddistributed network access device (e.g., DU 208 in FIG. 2). In the firstoption 505-a, an RRC layer 510 and a PDCP layer 515 may be implementedby the central unit, and an RLC layer 520, a MAC layer 525, and a PHYlayer 530 may be implemented by the DU. In various examples the CU andthe DU may be collocated or non-collocated. The first option 505-a maybe useful in a macro cell, micro cell, or pico cell deployment.

A second option 505-b shows a unified implementation of a protocolstack, in which the protocol stack is implemented in a single networkaccess device (e.g., access node (AN), new radio base station (NR BS), anew radio Node-B (NR NB), a network node (NN), or the like.). In thesecond option, the RRC layer 510, the PDCP layer 515, the RLC layer 520,the MAC layer 525, and the PHY layer 530 may each be implemented by theAN. The second option 505-b may be useful in a femto cell deployment.

Regardless of whether a network access device implements part or all ofa protocol stack, a UE may implement an entire protocol stack (e.g., theRRC layer 510, the PDCP layer 515, the RLC layer 520, the MAC layer 525,and the PHY layer 530).

FIG. 6 is a diagram 600 showing an example of a DL-centric subframe. TheDL-centric subframe may include a control portion 602. The controlportion 602 may exist in the initial or beginning portion of theDL-centric subframe. The control portion 602 may include variousscheduling information and/or control information corresponding tovarious portions of the DL-centric subframe. In some configurations, thecontrol portion 602 may be a physical DL control channel (PDCCH), asindicated in FIG. 6. The DL-centric subframe may also include a DL dataportion 604. The DL data portion 604 may sometimes be referred to as thepayload of the DL-centric subframe. The DL data portion 604 may includethe communication resources utilized to communicate DL data from thescheduling entity (e.g., UE or BS) to the subordinate entity (e.g., UE).In some configurations, the DL data portion 604 may be a physical DLshared channel (PDSCH).

The DL-centric subframe may also include a common UL portion 606. Thecommon UL portion 606 may sometimes be referred to as an UL burst, acommon UL burst, and/or various other suitable terms. The common ULportion 606 may include feedback information corresponding to variousother portions of the DL-centric subframe. For example, the common ULportion 606 may include feedback information corresponding to thecontrol portion 602. Non-limiting examples of feedback information mayinclude an ACK signal, a NACK signal, a HARQ indicator, and/or variousother suitable types of information. The common UL portion 606 mayinclude additional or alternative information, such as informationpertaining to random access channel (RACH) procedures, schedulingrequests (SRs), and various other suitable types of information. Asillustrated in FIG. 6, the end of the DL data portion 604 may beseparated in time from the beginning of the common UL portion 606. Thistime separation may sometimes be referred to as a gap, a guard period, aguard interval, and/or various other suitable terms. This separationprovides time for the switch-over from DL communication (e.g., receptionoperation by the subordinate entity (e.g., UE)) to UL communication(e.g., transmission by the subordinate entity (e.g., UE)). One ofordinary skill in the art will understand that the foregoing is merelyone example of a DL-centric subframe and alternative structures havingsimilar features may exist without necessarily deviating from theaspects described herein.

FIG. 7 is a diagram 700 showing an example of an UL-centric subframe.The UL-centric subframe may include a control portion 702. The controlportion 702 may exist in the initial or beginning portion of theUL-centric subframe. The control portion 702 in FIG. 7 may be similar tothe control portion described above with reference to FIG. 6. TheUL-centric subframe may also include an UL data portion 704. The UL dataportion 704 may sometimes be referred to as the payload of theUL-centric subframe. The UL data portion may refer to the communicationresources utilized to communicate UL data from the subordinate entity(e.g., UE) to the scheduling entity (e.g., UE or BS). In someconfigurations, the control portion 702 may be a physical DL controlchannel (PDCCH).

As illustrated in FIG. 7, the end of the control portion 702 may beseparated in time from the beginning of the UL data portion 704. Thistime separation may sometimes be referred to as a gap, guard period,guard interval, and/or various other suitable terms. This separationprovides time for the switch-over from DL communication (e.g., receptionoperation by the scheduling entity) to UL communication (e.g.,transmission by the scheduling entity). The UL-centric subframe may alsoinclude a common UL portion 706. The common UL portion 706 in FIG. 7 maybe similar to the common UL portion 706 described above with referenceto FIG. 7. The common UL portion 706 may additionally or alternativelyinclude information pertaining to channel quality indicator (CQI),sounding reference signals (SRSs), and various other suitable types ofinformation. One of ordinary skill in the art will understand that theforegoing is merely one example of an UL-centric subframe andalternative structures having similar features may exist withoutnecessarily deviating from the aspects described herein.

In some circumstances, two or more subordinate entities (e.g., UEs) maycommunicate with each other using sidelink signals. Real-worldapplications of such sidelink communications may include public safety,proximity services, UE-to-network relaying, vehicle-to-vehicle (V2V)communications, Internet of Everything (IoE) communications, IoTcommunications, mission-critical mesh, and/or various other suitableapplications. Generally, a sidelink signal may refer to a signalcommunicated from one subordinate entity (e.g., UE1) to anothersubordinate entity (e.g., UE2) without relaying that communicationthrough the scheduling entity (e.g., UE or BS), even though thescheduling entity may be utilized for scheduling and/or controlpurposes. In some examples, the sidelink signals may be communicatedusing a licensed spectrum (unlike wireless local area networks, whichtypically use an unlicensed spectrum).

A UE may operate in various radio resource configurations, including aconfiguration associated with transmitting pilots using a dedicated setof resources (e.g., a radio resource control (RRC) dedicated state,etc.) or a configuration associated with transmitting pilots using acommon set of resources (e.g., an RRC common state, etc.). Whenoperating in the RRC dedicated state, the UE may select a dedicated setof resources for transmitting a pilot signal to a network. Whenoperating in the RRC common state, the UE may select a common set ofresources for transmitting a pilot signal to the network. In eithercase, a pilot signal transmitted by the UE may be received by one ormore network access devices, such as an AN, or a DU, or portionsthereof. Each receiving network access device may be configured toreceive and measure pilot signals transmitted on the common set ofresources, and also receive and measure pilot signals transmitted ondedicated sets of resources allocated to the UEs for which the networkaccess device is a member of a monitoring set of network access devicesfor the UE. One or more of the receiving network access devices, or a CUto which receiving network access device(s) transmit the measurements ofthe pilot signals, may use the measurements to identify serving cellsfor the UEs, or to initiate a change of serving cell for one or more ofthe UEs.

Example Design for RSMA Modulated Streams

In wireless communications, multiple access technology allows severaluser devices to share one radio transmission resource. Over the pastseveral years, the innovation of multiple access technology has been anessential part of each new generation of cellular mobile systems.Various usage scenarios including enhanced mobile broadband (eMBB),massive machine type communications (mMTC), and ultra-reliable and lowlatency communications (URLLC) have been defined for 5G. Compared with4G systems, two of the key 5G capabilities are to provide higherconnection density and spectral efficiency. 4G cellular systems aremainly based on orthogonal multiple access (OMA) technologies. However,in recent years non-orthogonal multiple access has become an importantcandidate technology for 5G systems.

Non-orthogonal multiple access (NMA) allows the simultaneoustransmission of more than one layer of data for more than one UE withouttime, frequency or spatial domain separation. Different layers of datamay be separated by utilizing interference cancellation or iterativedetection at the receiver. NMA may be used to further enhance thespectral efficiency over OMA, in order to achieve the multiple UEchannel capacity. Furthermore, NMA may significantly increase the numberof UE connections, which is quite beneficial for 5G systems. Inaddition, NMA does not rely on the knowledge of instantaneous channelstate information (CSI) of frequency selective fading, and thus a robustperformance gain in practical wide area deployments may be expectedirrespective of UE mobility or CSI feedback latency. Uplink NMA schemeshave been studied in 3GPP RAN WG1 (working group 1). It has been agreedthat NMA should be investigated for diversified 5G usage scenarios anduse cases and 5G should target to support uplink NMA.

In an uplink NMA system, signal transmitter and receiver are jointlyoptimized, so that multiple layers of data from more than one UE can besimultaneously delivered in the same resource. At the transmitter side,the information of different UEs can be delivered using the same time,frequency and spatial resource. At the receiver side, the information ofdifferent UEs can be recovered by advanced receivers such asinterference cancellation or iterative detection receivers.

A number of NMA schemes have been proposed in RAN 1 meetings. Thedifference between these schemes is mainly on UE's signature design,i.e., whether a scrambling sequence, interleaver or spreading code isused to differentiate between UEs. Thus, the three main categories ofNMA schemes include scrambling based NMA schemes, interleaving based NMAschemes, and spreading based NMA schemes.

A key characteristic of the scrambling based NMA schemes is thatdifferent scrambling sequences are used to distinguish between differentUEs, and that an successive interference cancellation (SIC) algorithm isapplied at the BS receiver to separate different UEs. Resource SpreadMultiple Access (RSMA) is one example of a scrambling based NMA scheme.In RSMA, a group of different UEs' signals are super positioned on topof each other, and each UE's signal is spread to the entirefrequency/time resource assigned for the group. Different UEs' signalswithin the group are not necessarily orthogonal to each other and couldpotentially cause inter-UE interference. Spreading of bits to the entireresources enables decoding at a signal level below background noise andinterference. RSMA uses the combination of low rate channel codes andscrambling codes with good correlation properties to separate differentUEs' signals. Depending on application scenarios, the RSMA includessingle carrier RSMA and multi-carrier RSMA.

FIG. 8 illustrates an example design 800 for generating a multi-layerRSMA modulated stream. As shown, one or more transport blocks (TBs) 802are segmented 804 and assigned to different data sub-streams (806-1 to806-L). Each data sub-stream (806-1 to 806-L) is separately encoded(808-1 to 808-L). In an aspect, the one or more transport blocks maybecommonly encoded before segmentation and assignment to different datasub-streams. At 810, each encoded data sub-stream is mapped to one ormore RSMA layers based on a multi-layer RSMA layer mapping scheme. Forexample, each encoded sub-stream is mapped to a single and differentlayer (one to one mapping), each encoded stream is mapped to multiplelayers (one to many mapping), multiple encoded sub-streams are mapped toone layer, or a combination of the above. The RSMA layer mapping isfollowed by rate matching 812, modulation 814 and modulation symbolrepetition 816 (e.g., spreading). In an aspect, the modulation symbolrepetition 816 includes repeating the modulation symbols by a spreadingfactor (SF). For example, if the SF=X, the modulation symbols are spreadX times. In an aspect, the spreading factor may be the same or differentacross different RSMA layers or sub-layers. The modulation symbols ofeach sub-layer are then scrambled at 818 by a sub-layer pseudo-random(PN) scrambling sequence. Each sub-layer may be scrambled with the sameor different scrambling sequence. A sub-layer (PN) sequence for eachlayer or sub-layer may include repetition of an orthogonal code (e.g.,with permutation). In an aspect, the orthogonal code is generally ashort code which is extended by repeating the code or repeating the codewith permutation across layers. In an aspect, if the number of layers orsub-layers is larger than the number of orthogonal code sequences,repetition of quasi-orthogonal sub-layer code (e.g., with permutation)may be performed. In an aspect, quasi-orthogonal code includes Welchbound achieving code.

An additional phase rotation/power scaling factor g_(i) may be appliedat 820. The modulation symbols of the different sublayers maysynchronized and added at 822 and an outer scrambling of the addedmodulation symbol stream may be performed at 824. In an aspect, theouter scrambling includes scrambling the added modulation symbol streamusing an outer pseudo-random scrambling sequence. In an aspect, theouter PN scrambling sequence is different from the sub-layer PNscrambling sequences.

In certain aspects, in a single TB case, a single TB is segmented intomultiple data streams and the multi-layer RSMA layer mapping includesmapping each data stream to a different RSMA layer (e.g., one to onemapping).

In certain aspects, in a multiple TB case, multiple TBs may be assignedto different data streams. In an aspect, the multi-layer RSMA layermapping includes mapping each data stream to a different RSMA layer(e.g., one to one mapping). In an aspect, spreading the modulationsymbols of each sub-layer or layer may include applying the same number(X-times) of repetitions of modulation symbols across the multiple RSMAlayers. As noted above, the sub-layer PN sequence for each layer orsub-layer may be a repetition of a short code of X length (e.g., shortcode is quasi-orthogonal or orthogonal).

In certain aspects, the multi-layer RSMA layer mapping includes mappingeach data stream to a multiple RSMA layers (e.g., one to many mapping).The number of repetitions (X-times) of modulation symbols may bedifferent across the multiple RSMA layers or sub-layers.

In certain aspects, several different uplink multiplexing scenarios maybe considered for non-orthogonal multiple access (NMA). One example NMAscheme may include a grantless NMA scheme that does not include networkassignments or grants of scrambling sequences. For example, thesub-layer scrambling sequences and the outer scrambling sequence (asshown in FIG. 8) are not assigned by the network (e.g., gNB), but areselected by the UE. In an aspect, this type of NMA may relate to mMTCscenarios. In certain aspects, since scrambling sequences are notassigned by the network, a random multi-user (MU) codebook may be usedby a UE for scrambling in a grantless NMA.

In certain aspects, another example NMA scheme may include a grant basedNMA scheme that includes network assignment of scrambling sequences. Inan aspect, CSI may not be available at the gNB for the grant based NMA.In an aspect, this type of NMA may relate to a URLLC scenario in whichSRS and delay may be crucial and the UE may send only short packets, andthus CSI may not be available. In an aspect, the grant based NMA mayalso relate to eMBB in RRC-idle state, for example, where the UE hasbeen in an idle state for a while, and thus, CSI is not available. Thegrant based NMA may use a fixed MU codebook assigned by the network.

Certain aspects of the present disclosure discuss a two stage techniquefor generating, transmitting and decoding RSMA modulated streamsincluding multi-layer RSMA modulated streams. These techniques include atwo stage technique for generating, transmitting and decoding RSMAmodulated streams including multi-layer RSMA streams on the uplink. Inan aspect, the two stage technique includes two separate stages ofscrambling one or more data streams, the two stages using differenttypes of scrambling sequences with different lengths. In certainaspects, the two stage scrambling design for RSMA modulated streams maybe used for both grant based and grantless scenarios.

Example Sequence Based Short Code Design for Resource Spread MultipleAccess (RSMA)

Aspects of the present disclosure provide design that allows forassigning code sequences for UEs for use in RSMA. For example, the codedesign may be used for RSMA deployments described above, for example,whether using single or multiple scrambling stages.

FIG. 9 illustrates example operations 900 that may be performed by abase station (e.g., a gNB) to generate and assign code sequences to aset of UEs for RSMA.

Operations 900 begin, at 902, by assigning a set of sequences to a setof user equipments (UEs), wherein the set of sequences is designed tomeet one or more criteria for low cross correlation across the sequencesin the set and depends on a spreading factor (SF) and number of UEs (N).In some cases, the gNB may signal information to the UEs regarding theset of sequences. The UEs may receive and use this information to selector generate a scrambling sequence for RSMA transmission.

At 904, the base gNB receives a signal including transmissions from oneor more of the set of UEs, wherein each transmission from a UE isscrambled using one of the sequences in the set as a scramblingsequence. At 906, the gNB determines, for each transmission, thescrambling sequence.

At 908, the gNB decodes each transmission based on the determinedscrambling sequence. In some cases, the decoding involves distinguishing(identifying) at least one of different UEs or transmission layers,based on the different sequences in the set used for scrambling thetransmissions.

FIG. 10 illustrates example operations 1000 that may be performed by aUE, for example, to perform RSMA with a base station (e.g., a gNB)performing operations 900.

Operations 1000 begin, at 1002, by selecting a scrambling sequence, froma set of sequences designed to meet one or more criteria for low crosscorrelation across the sequences in the set and depends on a spreadingfactor (SF) and number of UEs (N) in a set of UEs including the UE. At1004, the UE uses the selected scrambling sequence to scramble antransmission to a base station.

In some cases, different UEs (e.g., UEs 1 and 2) are assigned differentspreading factors, namely SF1 and SF2 respectively. Thus, data streamsfor the UEs 1 and 2 are spread based on their respective assigned SFs.In a first scrambling stage, each layer of a particular UE (e.g., UE 1and 2) is assigned a different short code that corresponds to therespective assigned SF for the UE. The different short codes serve todistinguish the multiple layers of the same UE. As shown, the firstlayer of UE1 is assigned layer idx0 corresponding to SF1 and the secondlayer of UE1 is assigned layer idxl corresponding to SF1. Similarly, thefirst layer of UE2 is assigned idx0 corresponding to SF2 and the secondlayer of UE2 is assigned layer idxl corresponding to SF2. The parameters“Layer 1” and “Layer 2” represent different total number of layerscorresponding to SF 1 and SF2 respectively.

In a second scrambling stage, each scrambled modulation symbol stream(from the first stage) for each RSMA layer of a particular UE isscrambled again by a common UE-specific long sequence (e.g., eachUE-specific scrambling sequence may be longer than the sequences in theset of sequences to support overloading to support more UEs thanavailable resources). Different UE-specific long sequences are used forthe UEs 1 and 2. Thus, while the different long sequences are used todistinguish transmissions from the different UEs, different short codesare used to distinguish between layers of a particular UE.

In some cases, scrambling sequence may allow the base station todistinguish at least one of different UEs or transmission layers, basedon the different sequences in the set used for scrambling thetransmissions.

In some cases, the code sequence design may be used for short scramblingcodes described above and may be designed to have certain properties.For example, the code sequences may be designed such that a squared sumof cross correlation across sequences in the set achieves a fundamentallimit or such that individual sequence cross-correlation of each pair ofsequences in the set achieves a fundamental limit.

In certain aspects, the scrambled modulation symbol streams from thefirst scrambling stage for each layer of a particular UE may be addedbefore scrambling the added scrambled stream by a long sequence in thesecond scrambling stage.

FIG. 11 illustrates an example Chu-based short sequence design for 7 UEs(N=7) with a spreading factor of 4 (SF=4). In general, each sequence inthe set may be a truncated Chu sequence generated based on SF, N, and asequence index.

FIG. 12 illustrates the sequences for the 7 different indices, whileFIG. 13 shows the example cross-correlation matrix across sequences. Asillustrated in FIG. 14, in this example, the squared sum ofcross-correlation is equivalent to a fundamental limit (Welch bound),indicating this particular design may be desirable. FIG. 15 illustratesa fundamental equation for generating the sequences for the example N=7and SF=4.

FIG. 16 illustrates an example Chu-based short sequence design for 6 UEs(N=6) with a spreading factor of 4 (SF=4). FIG. 17 illustrates thesequences for the 6 different indices, while FIG. 18 shows the examplecross-correlation matrix across sequences. As illustrated in FIG. 19, inthis example, the squared sum of cross-correlation is not equivalent tothe fundamental limit (Welch bound), indicating this particular designmay not be desirable. FIG. 20 illustrates a fundamental equation forgenerating the sequences for the example N=6 and SF=4.

FIG. 21 illustrates the general equation for N and SF. Based on theequation and corresponding sequences, the tables shown in FIGS. 22through 26 may be generated for different combinations of K and Npopulated with the corresponding values of cross correlation compared tothe theoretical limit. Combinations that result in a match between theactual value and theoretical limit are highlighted as red.

As described above, certain aspects of the present disclosure provide aChu-Sequence Based design. In some cases, desirable sequences may beselected that achieve, for a given combination of N and K (SF), an exactSquared-Sum Welch bound achieving (sometime pairwise/element-wise boundtoo). As shown in the tables above, only a limited set of (N,K) meetdesirable property and may be used to achieve a constant Amplitude-lowPAPR. The sequences may also be generated with a closed form formula,meaning relatively small amount of storage is required.

Using the techniques described herein, for a (N,K) pair, which we canachieve the fundamental Welch bound, the satisfying proposed sequencecan be used.

Phase rotation and permutation of sequences may be equivalent, providingsome flexibility. Only certain pairs of values of SF and N may satisfythe criteria.

For the remaining (N,K) pairs, where the fundamental Welch bound is notachievable, there are various options. According to one option, aportion (subset) of sequences from a pair (N1,K) which achieves theWelch bound. (Here N1>N). As an example, as described above, the pair(6,4) does not achieve the fundamental limit, so the first 6 sequencesfrom (7,4) could be used.

According to another option, computer generated sequences (CGSs) withsmall cross correlation may be used. For K=2, QPSK sequences may beused:

For (N=2,K=2), (1, −1), (1, 1)

For (N=4,K=2), (1, −1), (1, 1), (1, −j), (1, j)

In some cases, the closed form formula shown in FIG. 21 may begeneralized further, as shown in FIG. 27, to include an offset F. Inother words, FIG. 21 may be considered the case where F=0. Non-zerooffsets can be chosen for specific values of (N, K).

For example, FIG. 28 illustrates an example for N=6 and K=4, and OffsetF=1. FIG. 29 illustrates the sequences for the 6 different indices,while FIG. 30 shows the example cross-correlation matrix acrosssequences. As illustrated in FIG. 31, in this example, the squared sumof cross-correlation is equivalent to a fundamental limit (Welch bound),indicating this particular design may be desirable.

FIG. 32 illustrates a fundamental equation for generating the sequencesfor this example for N=6, SF=4, and F=1.

FIG. 33 shows the table of the Squared Sum of Cross Correlation valuesachievable for different values of N, for K=4 and F=1. As already notedabove, with offset=1, for K=4, and N=6, the theoretic limit can beachieved (as with N=8, N=10, and N=11).

The methods disclosed herein comprise one or more steps or actions forachieving the described method. The method steps and/or actions may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isspecified, the order and/or use of specific steps and/or actions may bemodified without departing from the scope of the claims.

Moreover, the term “or” is intended to mean an inclusive “or” ratherthan an exclusive “or.” That is, unless specified otherwise, or clearfrom the context, the phrase, for example, “X employs A or B” isintended to mean any of the natural inclusive permutations. That is, forexample the phrase “X employs A or B” is satisfied by any of thefollowing instances: X employs A; X employs B; or X employs both A andB. As used herein, reference to an element in the singular is notintended to mean “one and only one” unless specifically so stated, butrather “one or more.” For example, the articles “a” and “an” as used inthis application and the appended claims should generally be construedto mean “one or more” unless specified otherwise or clear from thecontext to be directed to a singular form. Unless specifically statedotherwise, the term “some” refers to one or more. A phrase referring to“at least one of” a list of items refers to any combination of thoseitems, including single members. As an example, “at least one of: a, b,or c” is intended to cover: a, b, c, a-b, a-c, b-c, and a-b-c, as wellas any combination with multiples of the same element (e.g., a-a, a-a-a,a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c or anyother ordering of a, b, and c). As used herein, including in the claims,the term “and/or,” when used in a list of two or more items, means thatany one of the listed items can be employed by itself, or anycombination of two or more of the listed items can be employed. Forexample, if a composition is described as containing components A, B,and/or C, the composition can contain A alone; B alone; C alone; A and Bin combination; A and C in combination; B and C in combination; or A, B,and C in combination.

As used herein, the term “determining” encompasses a wide variety ofactions. For example, “determining” may include calculating, computing,processing, deriving, investigating, looking up (e.g., looking up in atable, a database or another data structure), ascertaining and the like.Also, “determining” may include receiving (e.g., receiving information),accessing (e.g., accessing data in a memory) and the like. Also,“determining” may include resolving, selecting, choosing, establishingand the like.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the language claims. All structural and functional equivalents tothe elements of the various aspects described throughout this disclosurethat are known or later come to be known to those of ordinary skill inthe art are expressly incorporated herein by reference and are intendedto be encompassed by the claims. Moreover, nothing disclosed herein isintended to be dedicated to the public regardless of whether suchdisclosure is explicitly recited in the claims.

The various operations of methods described above may be performed byany suitable means capable of performing the corresponding functions.The means may include various hardware and/or software component(s)and/or module(s), including, but not limited to a circuit, anapplication specific integrated circuit (ASIC), or processor. Generally,where there are operations illustrated in figures, those operations mayhave corresponding counterpart means-plus-function components.

For example, operations 900 of FIG. 9 may be performed by one or more ofa transmit processor 420, a TX MIMO processor 430, a receive processor438, or antenna(s) 434 of the base station 110, while operations 1000 ofFIG. 10 may be performed by the transmit processor 464, a TX MIMOprocessor 466, a receive processor 458, or antenna(s) 452 of the userequipment 120.

The various illustrative logical blocks, modules and circuits describedin connection with the present disclosure may be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array (FPGA) or other programmable logic device (PLD),discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general-purpose processor may be a microprocessor, but in thealternative, the processor may be any commercially available processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

If implemented in hardware, an example hardware configuration maycomprise a processing system in a wireless node. The processing systemmay be implemented with a bus architecture. The bus may include anynumber of interconnecting buses and bridges depending on the specificapplication of the processing system and the overall design constraints.The bus may link together various circuits including a processor,machine-readable media, and a bus interface. The bus interface may beused to connect a network adapter, among other things, to the processingsystem via the bus. The network adapter may be used to implement thesignal processing functions of the PHY layer. In the case of a userterminal 120 (see FIG. 1), a user interface (e.g., keypad, display,mouse, joystick, etc.) may also be connected to the bus. The bus mayalso link various other circuits such as timing sources, peripherals,voltage regulators, power management circuits, and the like, which arewell known in the art, and therefore, will not be described any further.The processor may be implemented with one or more general-purpose and/orspecial-purpose processors. Examples include microprocessors,microcontrollers, DSP processors, and other circuitry that can executesoftware. Those skilled in the art will recognize how best to implementthe described functionality for the processing system depending on theparticular application and the overall design constraints imposed on theoverall system.

If implemented in software, the functions may be stored or transmittedover as one or more instructions or code on a computer readable medium.Software shall be construed broadly to mean instructions, data, or anycombination thereof, whether referred to as software, firmware,middleware, microcode, hardware description language, or otherwise.Computer-readable media include both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. The processor may beresponsible for managing the bus and general processing, including theexecution of software modules stored on the machine-readable storagemedia. A computer-readable storage medium may be coupled to a processorsuch that the processor can read information from, and write informationto, the storage medium. In the alternative, the storage medium may beintegral to the processor. By way of example, the machine-readable mediamay include a transmission line, a carrier wave modulated by data,and/or a computer readable storage medium with instructions storedthereon separate from the wireless node, all of which may be accessed bythe processor through the bus interface. Alternatively, or in addition,the machine-readable media, or any portion thereof, may be integratedinto the processor, such as the case may be with cache and/or generalregister files. Examples of machine-readable storage media may include,by way of example, RAM (Random Access Memory), flash memory, phasechange memory, ROM (Read Only Memory), PROM (Programmable Read-OnlyMemory), EPROM (Erasable Programmable Read-Only Memory), EEPROM(Electrically Erasable Programmable Read-Only Memory), registers,magnetic disks, optical disks, hard drives, or any other suitablestorage medium, or any combination thereof. The machine-readable mediamay be embodied in a computer-program product.

A software module may comprise a single instruction, or manyinstructions, and may be distributed over several different codesegments, among different programs, and across multiple storage media.The computer-readable media may comprise a number of software modules.The software modules include instructions that, when executed by anapparatus such as a processor, cause the processing system to performvarious functions. The software modules may include a transmissionmodule and a receiving module. Each software module may reside in asingle storage device or be distributed across multiple storage devices.By way of example, a software module may be loaded into RAM from a harddrive when a triggering event occurs. During execution of the softwaremodule, the processor may load some of the instructions into cache toincrease access speed. One or more cache lines may then be loaded into ageneral register file for execution by the processor. When referring tothe functionality of a software module below, it will be understood thatsuch functionality is implemented by the processor when executinginstructions from that software module.

Also, any connection is properly termed a computer-readable medium. Forexample, if the software is transmitted from a website, server, or otherremote source using a coaxial cable, fiber optic cable, twisted pair,digital subscriber line (DSL), or wireless technologies such as infrared(IR), radio, and microwave, then the coaxial cable, fiber optic cable,twisted pair, DSL, or wireless technologies such as infrared, radio, andmicrowave are included in the definition of medium. Disk and disc, asused herein, include compact disc (CD), laser disc, optical disc,digital versatile disc (DVD), floppy disk, and Blu-ray® disc where disksusually reproduce data magnetically, while discs reproduce dataoptically with lasers. Thus, in some aspects computer-readable media maycomprise non-transitory computer-readable media (e.g., tangible media).In addition, for other aspects computer-readable media may comprisetransitory computer-readable media (e.g., a signal). Combinations of theabove should also be included within the scope of computer-readablemedia.

Thus, certain aspects may comprise a computer program product forperforming the operations presented herein. For example, such a computerprogram product may comprise a computer-readable medium havinginstructions stored (and/or encoded) thereon, the instructions beingexecutable by one or more processors to perform the operations describedherein.

Further, it should be appreciated that modules and/or other appropriatemeans for performing the methods and techniques described herein can bedownloaded and/or otherwise obtained by a user terminal and/or basestation as applicable. For example, such a device can be coupled to aserver to facilitate the transfer of means for performing the methodsdescribed herein. Alternatively, various methods described herein can beprovided via storage means (e.g., RAM, ROM, a physical storage mediumsuch as a compact disc (CD) or floppy disk, etc.), such that a userterminal and/or base station can obtain the various methods uponcoupling or providing the storage means to the device. Moreover, anyother suitable technique for providing the methods and techniquesdescribed herein to a device can be utilized.

It is to be understood that the claims are not limited to the preciseconfiguration and components illustrated above. Various modifications,changes and variations may be made in the arrangement, operation anddetails of the methods and apparatus described above without departingfrom the scope of the claims.

What is claimed is:
 1. A method of wireless communication by a BaseStation (BS), comprising: assigning a set of sequences to a set of userequipments (UEs), wherein: the set of sequences is designed to meet oneor more criteria for low cross correlation across sequences in the setof sequences; and sequences in the set of sequences are generated usingat least a spreading factor (SF) and a value representing a number ofUEs (N) in the set of UEs; receiving a signal including transmissionsfrom one or more of the set of UEs, wherein each transmission from a UEis scrambled using one of the sequences in the set as a scramblingsequence; determining, for each transmission, the scrambling sequence;and decoding each transmission based on the determined scramblingsequence.
 2. The method of claim 1, wherein the decoding comprisesdistinguishing at least one of different UEs or transmission layers,based on different sequences in the set of sequences used for scramblingthe transmissions.
 3. The method of claim 2, wherein the decodingfurther comprises: determining, for each transmission, a UE-specificscrambling sequence used to further scramble the transmission; andidentifying each UE based on the UE-specific scrambling sequence.
 4. Themethod of claim 3, wherein each UE-specific scrambling sequence islonger than the sequences in the set of sequences.
 5. The method ofclaim 1, wherein the one or more criteria comprises at least one of: asquared sum of cross correlation across sequences in the set achieving afundamental limit; or individual sequence cross-correlation of each pairof sequences in the set achieving a fundamental limit.
 6. The method ofclaim 5, wherein each sequence in the set comprises a truncated Chusequence generated based on SF, N, and a sequence index.
 7. The methodof claim 5, wherein: only certain pairs of values of SF and N satisfythe criteria; and for remaining pairs of SF and N, the set of sequencescomprises a subset of sequences from a set of sequences for one of thecertain pairs.
 8. The method of claim 5, wherein: only certain pairs ofvalues of SF and N satisfy the criteria when the sequences comprisetruncated Chu sequences; and for remaining pairs of SF and N, the set ofsequences comprises computer generated sequences (CGSs).
 9. The methodof claim 1, wherein: different sets of UEs are assigned different setsof sequences, based on at least one of: the number of UEs in the set ora number of transmission layers.
 10. The method of claim 1, furthercomprising signaling information regarding the set of sequences to theset of UEs.
 11. A method of wireless communication by a user equipment(UE), comprising: selecting a scrambling sequence, from a set ofsequences designed to meet one or more criteria for low crosscorrelation across sequences in the set of sequences, wherein sequencesin the set of sequences were generated using at least a spreading factor(SF) and a value representing a number of UEs (N) in a set of UEsincluding the UE; and using the selected scrambling sequence to scramblea transmission to a base station.
 12. The method of claim 11, whereinthe selected scrambling sequence allows for distinguishing at least oneof different UEs or transmission layers.
 13. The method of claim 12,further comprising: using a UE-specific scrambling sequence to furtherscramble the transmission.
 14. The method of claim 13, wherein eachUE-specific scrambling sequence is longer than the sequences in the setof sequences.
 15. The method of claim 11, wherein the one or morecriteria comprises at least one of: a squared sum of cross correlationacross sequences in the set achieving a fundamental limit; or individualsequence cross-correlation of each pair of sequences in the setachieving a fundamental limit.
 16. The method of claim 15, wherein eachsequence in the set comprises a truncated Chu sequence generated basedon SF, N, and a sequence index.
 17. The method of claim 15, wherein:only certain pairs of values of SF and N satisfy the criteria; and forremaining pairs of SF and N, the set of sequences comprises a subset ofsequences from a set of sequences for one of the certain pairs.
 18. Themethod of claim 15, wherein: only certain pairs of values of SF and Nsatisfy the criteria when the sequences comprise truncated Chusequences; and for remaining pairs of SF and N, the set of sequencescomprises computer generated sequences (CGSs).
 19. The method of claim11, further comprising: receiving signaling information regarding theset of sequences to the set of UEs; and using the information to atleast one of select or generate the scrambling sequence.
 20. The methodof claim 11, further comprising signaling information regarding the setof sequences to the base station.
 21. An apparatus for wirelesscommunication by a base station (BS), comprising: means for assigning aset of sequences to a set of user equipments (UEs), wherein: the set ofsequences is designed to meet one or more criteria for low crosscorrelation across sequences in the set of sequences; and sequences inthe set of sequences are generated using at least a spreading factor(SF) and a value representing a number of UEs (N); means for receiving asignal including transmissions from one or more of the set of UEs,wherein each transmission from a UE is scrambled using one of thesequences in the set as a scrambling sequence; means for determining,for each transmission, the scrambling sequence; and means for decodingeach transmission based on the determined scrambling sequence.
 22. Anapparatus for wireless communication by a user equipment (UE),comprising: means for selecting a scrambling sequence, from a set ofsequences designed to meet one or more criteria for low crosscorrelation across sequences in the set of sequences, wherein sequencesin the set of sequences were generated using at least a spreading factor(SF) and a value representing a number of UEs (N) in a set of UEsincluding the UE; and means for using the selected scrambling sequenceto scramble a transmission to a base station.